Nagasaki marks 70th anniversary of bomb

Doves fly over the Peace Statue in Nagasaki's Peace Park during a ceremony commemorating the 70th anniversary (Reuters)

Japan has marked the 70th anniversary of the atomic bombing of Nagasaki that claimed more than 74,000 lives almost instantly, in one of the final chapters of World War II.

Bells tolled and tens of thousands of people, including ageing survivors and the relatives of victims, observed a minute's silence on Sunday at 11:02am (local time), the exact moment the blast devastated the port city on August 9, 1945.

Prime Minister Shinzo Abe laid a wreath of flowers, with representatives from 75 countries, including US ambassador Caroline Kennedy, attending the ceremony.

"As the only country attacked with an atomic bomb in war, I am renewing our determination to lead the global effort of nuclear disarmament, to create a world without such weapons," Abe said in his speech.

Abe also said the country would continue to abide by its long-held non-nuclear principles: not producing, possessing or allowing nuclear weapons on Japanese territory.

He was criticised for failing to mention the three principles at a ceremony days earlier in Hiroshima, alarming atomic bomb survivors, particularly at a time when the nationalist leader is trying to push through legislation to expand the role of the military.

Nagasaki Mayor Tomihisa Taue appeared to implicitly criticise the bills in a speech at the ceremony.

"Worries and anxieties are now spreading among us that this pledge made 70 years ago and the principle for peace in the Japanese constitution may be now undermined," he said to loud applause.

A constitution imposed by US occupiers after the war prevented Japan's military from engaging in combat except in self defence.

About 74,000 people died in the initial blast in Nagasaki from a plutonium bomb dubbed "Fat Man", or from after-effects in the months and years after.

The attack on Nagasaki came three days after American B-29 bomber Enola Gay dropped a bomb, dubbed "Little Boy", on Hiroshima, the first atomic bombing in history.

Nearly everything around it was incinerated by a wall of heat up to 4,000 degrees Celsius - hot enough to melt steel.

About 140,000 people are estimated to have been killed in the Hiroshima attack, including those who survived the bombing itself but later died from radiation sickness.

The twin bombings dealt the final blows to imperial Japan, which surrendered on August 15, 1945, bringing an end to World War II.